Golf club head

ABSTRACT

A head  4  includes a head body m 1  and a recessed-part forming member b 1 . The head body m 1  includes an opening hs 1  for a recessed part, and a receiving part x 1  formed on at least a part of a periphery of the opening hs 1  for a recessed part. The recessed-part forming member b 1  is fixed to the opening hs 1  for a recessed part. A recessed part R is formed on an outer surface of the head by the recessed-part forming member b 1 . The recessed-part forming member b 1  is formed separately from the head body m 1 . The recessed-part forming member b 1  includes an outer extension part y 1 . The outer extension part y 1  is supported by the receiving part x 1 . The head  4  is hollow.

TECHNICAL FIELD

The present invention relates to a golf club head.

BACKGROUND ART

A hollow golf club head on which a recessed part, such as a groove and a boss hole, is provided has been known. The recessed part is provided on a sole, for example. There are various reasons for providing the recessed part. For example, a weight body can be disposed on the recessed part. The recessed part can also influence the position of the center of gravity of the head, rebound characteristic, and the like. The recessed part may be provided for the sake of design.

The recessed part can be formed by a known method. Examples of the method include casting and forging. US2010/0065240 discloses a manufacturing method for a wax mold. In the manufacturing method, a hole is provided on a wax shell, and a wax plug is inserted into the hole.

CITATION LIST Patent Literature

-   Patent Literature 1: US2010/0065240

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

As already mentioned, there are various reasons for providing a recessed part. It is preferable that a degree of freedom in design of the recessed part is high. However, the size and the shape of the recessed part can be restricted depending on the structure or the manufacturing method of a head.

It is an objective of the present invention to provide a golf club head having a recessed part and a high degree of freedom in design.

Solution to the Problems

A golf club head according to the present invention includes a head body and a recessed-part forming member. The head body has an opening for a recessed part, and a receiving part formed on the periphery of the opening for a recessed part. The recessed-part forming member is fixed to the opening for a recessed part. A recessed part is formed on an outer surface of the head by the recessed-part forming member. The recessed-part forming member is formed separately from the head body. The recessed-part forming member has an outer extension part. The outer extension part is supported by the receiving part.

Preferably, the head body includes a sole and a crown. Preferably, the head body is produced by casting. Preferably, the recessed-part forming member is attached to the sole. Preferably, a shortest distance T1 between the recessed-part forming member and the crown is equal to or less than 30 mm.

Preferably, the head further includes a weight body. Preferably, the weight body is disposed on the recessed part in a detachable state.

Preferably, the head further includes a socket. Preferably, the socket is fixed in the recessed part. Preferably, relative rotation of an angle θ can be performed between the weight body and the socket. Preferably, the rotation of the angle θ allows the weight body to be attached to the socket. Preferably, reverse rotation of the angle θ allows the weight body to be detached from the socket.

Advantageous Effects of the Invention

It is possible to provide a golf club head that has a recessed part and is excellent in a degree of freedom in design.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a head according to a first embodiment of the present invention. In FIG. 1, a weight body attaching/detaching mechanism is omitted.

FIG. 2 is across sectional perspective view taken along line F2-F2 in FIG. 1.

FIG. 3 is a cross sectional view of a vicinity of a recessed-part forming member.

FIG. 4 is a perspective view of the recessed-part forming member.

FIG. 5 is a cross sectional view of the recessed-part forming member.

FIG. 6 is a cross sectional view of a head body in the vicinity of the recessed-part forming member.

FIG. 7 is a cross sectional view of a vicinity of a recessed-part forming member according to a second embodiment.

FIG. 8 is a cross sectional view of a vicinity of a recessed-part forming member according to a third embodiment.

FIG. 9 is a perspective view of a head according to a fourth embodiment. In FIG. 9, a weight body attaching/detaching mechanism is omitted.

FIG. 10 is a cross sectional view taken along line F10-F10 in FIG. 9.

FIG. 11 is an exploded perspective view of a weight body attaching/detaching mechanism.

FIG. 12 is a perspective view of a socket.

FIG. 13 is a plan view, a cross sectional view, and a bottom view of the socket in FIG. 12.

FIG. 14 is an enlarged bottom view of the socket.

FIG. 15 is a plan view, a side view, and a bottom view of a weight body.

FIG. 16 shows a mutual transition of an engaging position EP and a non-engaging position NP.

FIG. 17 is a perspective view of a tool.

FIG. 18 (a) shows a state before the weight body is attached, FIG. 18( b) shows a state immediately after the weight body is inserted, and FIG. 18 (c) shows a state where the weight body is rotated and is fixed to the socket.

FIG. 19 is an exploded perspective view showing a modification of the weight body attaching/detaching mechanism.

FIG. 20 is a perspective view of a socket.

FIG. 21 is a plan view, a cross sectional view, and a bottom view of the socket in FIG. 20.

FIG. 22 is a cross sectional view of a weight body of a modification.

FIG. 23 is a cross sectional view of a head to which a weight body attaching/detaching mechanism is attached. The weight body of FIG. 22 is used in the weight body attaching/detaching mechanism in FIG. 23.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present invention will be described in detail according to the preferred embodiments with appropriate references to the accompanying drawings.

In the present application, a reference vertical plane, a face-back direction and a toe-heel direction are defined. A reference state denotes a state that the center axial line Z1 of a shaft is contained in a plane Pv perpendicular to a horizontal plane H and the head is placed on the horizontal plane H at a prescribed lie angle and real loft angle. The reference vertical plane denotes the plane Pv. The prescribed lie angle and real loft angle are appeared, for example, in a product catalog. The center axial line Z1 of the shaft conforms to a center axial line of a shaft hole.

In the present application, the toe-heel direction is a direction of an intersection line between the reference vertical plane and the horizontal plane H.

In the present application, the face-back direction is a direction perpendicular to the toe-heel direction and parallel to the horizontal plane H.

In the present application, a face center is defined. A maximum width Wx of a face surface in the toe-heel direction is determined. Furthermore, a middle position Px of the maximum width Wx in the toe-heel direction is determined. At the position Px, a middle point Py of the face surface in an up-down direction is determined. The point Py is defined as the face center.

FIG. 1 is a perspective view of a head 4 according to a first embodiment. FIG. 2 is a partial cross-sectional perspective view showing a cross section taken along line F2-F2 in FIG. 1.

The head 4 includes a face 5, a crown 6, a sole 8 and a hosel 9.

Although not shown in the drawings, the head 4 includes an attaching/detaching structure to a shaft. A hole N1 for fixing the shaft is provided on the sole 8. Although not shown in the drawings, a screw for fixing the shaft is inserted from the hole N1. Such an attaching/detaching structure has been known.

The sole 8 includes a recessed part R. In the embodiment, the number of the recessed parts R is plural. Two recessed parts R are provided. The sole 8 includes a first recessed part R1 and a second recessed part R2. The first recessed part R1 is provided on a toe side relative to the second recessed part R2. The second recessed part R2 is positioned on a back side of the hole N1.

The first recessed part R1 is positioned on the toe side relative to the face center. The second recessed part R2 is positioned on a heel side relative to the face center.

The recessed part R may not include a perfect bottom surface. A bottom part of the recessed part R may be passed through to a hollow part of the head.

The head 4 is a wood type head. The head 4 is exemplary. For example, a utility type head, a hybrid type head, an iron type head, and a putter type head may be used in place of the head 4.

As shown in FIG. 2, the head 4 is hollow.

The head 4 includes a head body m1. The head body m1 includes the crown 6 and the sole 8. The head body m1 also includes the hosel 9. The whole of the head body m1 is integrally formed. In the embodiment, the head body m1 is manufactured by casting.

The head body m1 may be manufactured by another manufacturing method. Examples of the manufacturing method include forging and a press. The head body m1 may be produced by joining a plurality of members.

The head body m1 includes a face opening hf. As shown in FIG. 2, a face plate fp is attached to the face opening hf.

FIG. 3 is an enlarged cross sectional view of the vicinity of the first recessed part R1. The head body m1 includes an opening hs1 for a recessed part. The opening hs1 for a recessed part is provided on the sole 8. A recessed-part forming member b1 is attached to the opening hs1 for a recessed part. The recessed-part forming member b1 is a separate member from the head body m1.

The recessed-part forming member b1 is positioned on the toe side relative to the face center.

The recessed-part forming member b1 is fixed to the opening hs1 for a recessed part. The fixation is attained by welding. Examples of other fixing methods include adhesion with an adhesive, and caulking. Multiple fixing methods may be used in combination.

The opening hs1 for a recessed part corresponds to the first recessed part R1. The first recessed part R1 is formed by the recessed-part forming member b1 attached to the opening hs1 for a recessed part.

The second recessed part R2 is a part of the integrally formed head body m1. The second recessed part R2 is integrally formed with the sole 8.

As shown in FIG. 3, the head body m1 includes a receiving part x1. The receiving part x1 is formed on a part or the whole of the periphery of the opening hs1 for a recessed part. In the embodiment, the receiving part x1 is formed on the whole periphery of the opening hs1 for a recessed part. In the embodiment, the receiving part x1 has a circular ring shape.

FIG. 4 is a perspective view of the recessed-part forming member b1. FIG. 5 is a cross sectional view of the recessed-part forming member b1. FIG. 6 is a cross sectional view of the head body m1 in the vicinity of the opening hs1 for a recessed part.

The recessed-part forming member b1 includes an outer extension part y1. The outer extension part y1 extends toward outside of the recessed part R from an edge part of an opening side of the recessed-part forming member b1. In the embodiment, the outer extension part y1 forms a flange.

Furthermore, the recessed-part forming member b1 includes a side surface part z1 and a bottom surface part bt. The side surface part z1 includes a first side surface part z1 a and a second side surface part z1 b. The first side surface part z1 a has an inner diameter lager than the inner diameter of the second side surface part z1 b. The first side surface part z1 a is positioned between the outer extension part y1 and the second side surface part z1 b.

The recessed-part forming member b1 is formed separately from the head body m1. The method for manufacturing the head body m1 is not limited. Examples of the method include casting, forging, and NC process.

As shown in FIG. 3, the outer extension part y1 is supported by the receiving part x1. The receiving part x1 is positioned inside the outer extension part y1. The inside means the inside of the head. The outer extension part y1 is supported from the inside by the receiving part x1.

An end face y1 a of the outer extension part y1 is flush with a surface 8 a of the sole 8. Smooth continuity between the end face y1 a and the surface 8 a may be accomplished by grinding. In this case, the end face y1 a and the surface 8 a are ground after the recessed-part forming member b1 is fixed to the opening hs1 for a recessed part.

The receiving part x1 serves a function of positioning the recessed-part forming member b1. When the recessed-part forming member b1 is joined to the head body m1, first, the recessed-part forming member b1 is disposed to the opening hs1 for a recessed part. Joining (such as welding) is performed in this state. Because of the existence of the receiving part x1, the recessed-part forming member b1 is positioned accurately, and a positional displacement of the recessed-part forming member b1 during work on the joining process is prevented. Therefore, the recessed-part forming member b1 can be fixed to an accurate position.

A force acts on the recessed-part forming member b1 in association with an impact force in hitting. The force includes a force Fx of a direction toward the inside of the head. The receiving part x1 effectively receives the force Fx acting on the recessed-part forming member b1. Therefore, the joining part between the recessed-part forming member b1 and the head body m1 has high durability.

A lower surface y1 b (see FIG. 5) of the outer extension part y1 abuts on an upper surface x1 a (see FIG. 6) of the receiving part x1. A side surface y1 c (see FIG. 5) of the outer extension part y1 abuts on a step surface x1 c (see FIG. 6) of the receiving part x1.

Weight bodies Wt1 are disposed on the first recessed part R1 and the second recessed part R2 in a detachable state, as will be discussed in detail later. In FIG. 1 and the like, the weight bodies Wt1 are omitted.

In the present application, a case where the recessed part R is integrally formed with the head body m1 is also referred to as a recessed-part integral forming. In the recessed-part integral forming, while the productivity of the head is increased, various problems can arise.

A lost-wax casting may be adopted as a method for manufacturing a head. In this case, a wax mold is produced, and then the lost-wax casting is performed. In the recessed-part integral forming, the depth and the size of the recessed part are restricted in forming the wax mold. Meanwhile, as US2010/0065240 described above, it can be considered to join the wax mold of the head body m1 and the wax mold of the recessed part. In this case, however, a problem of deteriorating molten metal flow to the recessed part arises, because the head body m1 is integral with the recessed part in the step of casting. Therefore, it is necessary to take a measure of downsizing the recessed part or thickening the recessed part and the periphery thereof for the purpose of improving molten metal flow.

In a head for a fairway wood, for example, the volume of the hollow part is small, and particularly, the height in the up-down direction of the hollow part is small, as compared with a head for a driver. In this case, the bottom surface of the recessed part is apt to come nearer to an inner surface of the head which is opposed to the bottom surface. If the recessed-part integral forming of the wax mold is performed in this state, it becomes difficult to extract a core.

Meanwhile, forging or a press may be adopted as the manufacturing method of the head. In this case, in the recessed-part integral forming, a draft angle is needed for the recessed part, and the shape of the recessed part is restricted. In addition, in forging or a press, the depth of the recessed part can be restricted. In the press, it is difficult to form a deep recessed part. In forging, although it is possible to form the recessed part having a certain degree of depth, the forging needs to be performed multiple times.

In the embodiment, these problems can be solved. The problems can be solved in any manufacturing methods of casting, forging and a press, because the recessed-part forming member b1 and the head body m1 are formed separately from each other.

FIG. 7 is a cross sectional view of a sole to which a recessed-part forming member b2 according to a second embodiment is attached. In the recessed-part forming member b2, the thickness ty1 of the outer extension part y1 is greater than an average thickness t1. The average thickness t1 is an average thickness of a portion of the recessed-part forming member b2 excluding the outer extension part y1. Joining strength of the recessed-part forming member b2 and the head body m1 is improved by increasing the thickness ty1. In addition, a position of the center of gravity of the recessed-part forming member b2 is shifted to a sole side by making the thickness ty1 greater than the thickness t1. This makes the position of the center of gravity of the head lowered. The low center of gravity of the head contributes to improve a flight distance performance.

By decreasing the thickness t1, room for additional weight is created to improve a degree of freedom in design of the position of the center of gravity of the head. A high strength is not needed for the bottom surface part bt and the vicinity thereof. Therefore, even when the thickness t1 is decreased, the influence to strength is small.

In respect of the strength of the recessed-part forming member b2, an average thickness ta of the whole recessed-part forming member b2 is equal to or greater than 0.7 mm, and more preferably equal to or greater than 1.0 mm. In consideration of the degree of freedom in design of the position of the center of gravity of the head, the weight of the recessed-part forming member b2 is preferably suppressed. In this respect, the whole average thickness ta is preferably equal to or less than 3.0 mm, more preferably equal to or less than 2.0 mm, and still more preferably equal to or less than 1.8 mm. When the average thickness ta is small, molten metal flow in casting is deteriorated. Thus, when the thickness ta is small, it is difficult to perform the recessed-part integral forming by casting.

In respect of the joining strength of the recessed-part forming member b2 and the head body m1, and suppression of the deformation of the recessed part R, the thickness ty1 is preferably equal to or greater than 1.0 mm, and more preferably equal to or greater than 1.1 mm. In respect of suppressing the weight of the recessed-part forming member b2, the thickness ty1 is preferably equal to or less than 1.5 mm, and more preferably equal to or less than 1.4 mm.

In respect of suppression of the deformation of the recessed part R, the average thickness t1 is preferably equal to or greater than 0.5 mm, more preferably equal to or greater than 0.6 mm, and still more preferably equal to or greater than 0.7 mm. In respect of suppressing the weight of the recessed-part forming member b2, the average thickness t1 is equal to or less than 1.2 mm, and more preferably equal to or less than 1.0 mm.

FIG. 8 is a cross sectional view of a sole to which a recessed-part forming member b3 according to a third embodiment is attached. A head body m3 includes a receiving part x3. The receiving part x3 has an inclined surface x31. The inclined surface x31 has a shape of a conical recess surface as a whole. The receiving part x3 is inclined so that an opening width thereof is widened toward outside of the head.

The recessed-part forming member b3 includes an outer extension part y3. The outer extension part y3 has a shape corresponding to the shape of the receiving part x3. The outer extension part y3 is supported by the receiving part x3. The outer extension part y3 includes an inclined surface y31. The inclined surface y31 has a shape of a conical protruded surface as a whole. The inclined surface y31 abuts on the inclined surface x31. The inclined surface y31 is brought into surface contact with the inclined surface x31. The inclined surface x31 and the inclined surface y31 further facilitate positioning the recessed-part forming member b3 in joining.

A double pointed arrow Db in FIG. 8 shows a length in a depth direction of the recessed-part forming member b3. By the above mentioned reason, when the length Db is large, the recessed-part integral forming is likely to become difficult. Therefore, when the length Db is large, an advantage of the embodiment can be increased. In this respect, the length Db is preferably equal to or greater than 8 mm, more preferably equal to or greater than 9 mm, and still more preferably equal to or greater than 10 mm. When the length Db is excessively large, the degree of freedom in design of the head is reduced. In this respect, the length Db is preferably equal to or less than 20 mm, more preferably equal to or less than 18 mm, and still more preferably equal to or less than 16 mm.

An outer edge of the recessed-part forming member b1 is shown by symbol k1 in FIG. 8 and the like. In the embodiment, the outer edge k1 is a boundary between a sole surface and the recessed-part forming member b1. In the embodiments of FIGS. 1, 8 and the like, the outer edge k1 has a circular shape. In these embodiments, a length Lk of the outer edge k1 is a length of the circumference of the circle.

By the above mentioned reason, as the recessed-part forming member b1 is larger, the recessed-part integral forming is likely to become difficult. Therefore, when the length Lk is large, an advantage of the embodiment can be increased. In this respect, the length Lk is preferably equal to or greater than 28 mm, more preferably equal to or greater than 30 mm, and still more preferably equal to or greater than 32 mm. When the length Lk is excessively large, the degree of freedom in design of the head is reduced. In this respect, the length Lk is preferably equal to or less than 80 mm, more preferably equal to or less than 65 mm, and still more preferably equal to or less than 50 mm.

FIG. 9 is a perspective view of a head 40 according to a fourth embodiment. In the head 40, a third recessed part R3 is provided as the recessed part R. The head 40 is the same as the head 4 except the existence of the third recessed part R3.

The third recessed part R3 has a groove shape. The longitudinal direction of the third recessed part R3 is a substantially toe-heel direction.

FIG. 10 is a cross sectional view taken along line F10-F10 in FIG. 9. FIG. 10 is an enlarged cross sectional view in the vicinity of the third recessed part R3. The head body m4 has an opening hs3 for a recessed part. The opening hs3 for a recessed part is provided on the sole 8. A recessed-part forming member b4 is attached to the opening hs3 for a recessed part. The recessed-part forming member b4 is a separate member from the head body m4.

The recessed-part forming member b4 is fixed to the opening hs3 for a recessed part. The fixation is attained by welding. Examples of other fixing methods include adhesion with an adhesive, and caulking. Multiple fixing methods may be used in combination.

The inside of the recessed-part forming member b4 is hollow. Therefore, an elastic deformation to be described later is apt to occur.

The opening hs3 for a recessed part corresponds to the third recessed part R3. The third recessed part R3 is formed by the recessed-part forming member b4 attached to the opening hs3 for a recessed part.

As shown in FIG. 10, the head body m4 includes a receiving part x4. The receiving part x4 is formed on the periphery of the opening hs3 for a recessed part. In the embodiment, the receiving part x4 has a long and narrow ring shape.

The recessed-part forming member b4 includes an outer extension part y4. The outer extension part y4 extends toward outside of the recessed part R3 from an edge part of an opening side of the recessed-part forming member b4.

Furthermore, the recessed-part forming member b4 includes a side surface part z4 and a bottom surface part bt4. The side surface part z4 smoothly continues to the bottom surface part bt4.

The recessed-part forming member b4 is formed separately from the head body m4. The method for manufacturing the recessed-part forming member b4 is not limited. Examples of the method include casting, forging, and NC process.

As shown in FIG. 10, the outer extension part y4 is supported by the receiving part x4. The receiving part x4 is positioned inside the outer extension part y4. The inside means the inside of the head. The outer extension part y4 is supported from the inside by the receiving part x4.

The receiving part x4 serves a function of positioning the recessed-part forming member b4. When the recessed-part forming member b4 is joined to the head body m4, first, the recessed-part forming member b4 is disposed to the opening hs3 for a recessed part. Joining (such as welding) is performed in this state. Because of the existence of the receiving part x4, the recessed-part forming member b4 is positioned accurately, and a positional displacement of the recessed-part forming member b4 during work on the joining process is prevented. Therefore, the recessed-part forming member b4 can be fixed to an accurate position.

A force acts on the recessed-part forming member b4 in association with an impact force in hitting. The force includes a force Fx of direction toward the inside of the head. The receiving part x4 effectively receives the force Fx acting on the recessed-part forming member b4. Therefore, at the joining between the recessed-part forming member b4 and the head body m4, high durability is exhibited.

A side surface y4 c of the outer extension part y4 abuts on a step surface x4 c of the receiving part x4.

A force acts on the recessed-part forming member b4 in association with an impact force in hitting. The force includes a compressive force Fy that narrows the width of the groove of the recessed-part forming member b4. The step surface x4 c of the receiving part x4 effectively receives the force Fy. Therefore, at the joining between the recessed-part forming member b4 and the head body m4, high durability is exhibited.

By the force Fy, the recessed-part forming member b4 is compressed and is elastically deformed. The elastic deformation involves restoration of the deformation. The elastic deformation improves rebound performance of the head. Because of the abutment of the side surface y4 c and the step surface x4 c, the force Fy is effectively conveyed to the recessed-part forming member b4, and the elastic deformation is facilitated. Therefore, the rebound performance of the head is enhanced.

In respect of enhancing the rebound performance, a toe-heel directional length Lb4 of the recessed part R formed by the recessed-part forming member b4 is preferably equal to or greater than 30 mm, more preferably equal to or greater than 40 mm, and still more preferably equal to or greater than 50 mm. Because of restriction on the size of the head, the length Lb4 is preferably equal to or less than 90 mm, more preferably equal to or less than 80 mm, and still more preferably equal to or less than 70 mm.

In consideration of the rebound performance, the recessed part formed by the recessed-part forming member b4 preferably has a shape of a groove. In this respect, a width Wb4 of the recessed-part forming member b4 is equal to or less than 25 mm, more preferably equal to or less than 20 mm, and still more preferably equal to or less than 15 mm. The width Wb4 is measured along a face-back direction.

The recessed-part forming member b4 is positioned on a face side relative to the first recessed part R1. The recessed-part forming member b4 is positioned on the face side relative to the second recessed part R2. As will be discussed later, the weight bodies Wt1 are disposed on the first recessed part R1 and the second recessed part R2. Therefore, the recessed-part forming member b4 is positioned between the face 5 and the weight bodies Wt1. The positional relationship facilitates the elastic deformation of the recessed-part forming member b4 in hitting. This is because a force from a ball acts on the face 5, and mass is concentrated on the weight bodies Wt1. The mass concentration parts have a great inertia. For this reason, the force Fy is apt to increase in a region between the mass concentration parts and the face 5. The increased force Fy facilitates the elastic deformation of the recessed-part forming member b4, and thereby the rebound performance of the head is enhanced.

As shown in FIG. 10, the cross section along the face-back direction of the recessed-part forming member b4 is smoothly continuous. The cross section along the face-back direction of the recessed-part forming member b4 does not include a corner part. Therefore, a stress concentration is relieved in the elastic deformation. Therefore, the recessed-part forming member b4 has a high durability against repeated elastic deformations.

As mentioned above, the weight body Wt1 is disposed on the first recessed part R1 and the second recessed part R2. The weight body Wt1 is detachably disposed. Examples of the attachable/detachable structure include a screw connection in addition to a weight body attaching/detaching mechanism M1 to be described later.

The weight body attaching/detaching mechanism M1 is attached to the first recessed part R1. The weight body attaching/detaching mechanism M1 is also attached to the second recessed part R2. Hereinafter, explanations are given citing the first recessed part R1 as an example.

FIG. 11 is an exploded perspective view of the weight body attaching/detaching mechanism M1. The weight body attaching/detaching mechanism M1 includes a socket sk1 and the weight body Wt1. The shape of the socket sk1 corresponds to the shape of the recessed part R1. In other words, the shape of the socket sk1 corresponds to the inner shape of the recessed-part forming member b1.

The socket sk1 is fixed in the recessed-part forming member b1. The fixation is attained by, for example, an adhesive. The weight body Wt1 is detachably attached to the socket sk1. Therefore, the weight body Wt1 can be detachably attached to the head 4.

In the embodiment, a plurality of weight body attaching/detaching mechanisms M1 is provided. In the head 4, two weight body attaching/detaching mechanisms M1 are provided. The number of the weight body attaching/detaching mechanisms M1 is not limited. The position of the weight body attaching/detaching mechanism M1 is not limited.

FIG. 12 is a perspective view of the socket sk1. FIG. 12 is a perspective view from a bottom face side. FIG. 13 shows a plan view of the socket sk1, a cross sectional view of the socket sk1, and a bottom view of the socket sk1 in this order from the top. FIG. 14 is an enlarged view of the bottom view of FIG. 13. As shown in FIGS. 12 and 13, the socket sk1 has a hole 16.

The hole 16 has a first hole part 18, a second hole part 20, and a step surface 22. A side surface 24 of the socket sk1 is a cylindrical surface. The hole 16 extends through the socket sk1. The hole 16 may not extend through the socket sk1. The whole inner surface of the first hole part 18 smoothly continues. The whole inner surface of the second hole part 20 smoothly continues.

The sectional shape (see the plan view of FIG. 13) of the first hole part 18 is substantially equal to that of an engaging part 32 of the weight body Wt1. In the embodiment, the sectional shape of the first hole part 18 and the sectional shape of the engaging part 32 are substantially squares. These substantial squares are obtained by applying roundness to four corners of the square. It is preferable that a length L1 of the second hole part 20 is substantially equal to a length L11 of the engaging part 32 of the weight body Wt1, or is shorter than the length L11.

Preferably, the material of the socket sk1 is a polymer. The polymer is comparatively hard. When the weight body Wt1 is attached/detached, the polymer can be elastically deformed. The attaching/detaching scheme will be described later. The structure of the second hole part 20 of the hole 16 will also be described later.

FIG. 15 shows a plan view, a side view, and a bottom view of the weight body Wt1 in this order from the top. As shown in FIG. 15, the weight body Wt1 has a head part 28, a neck part 30, and the engaging part 32. The neck part 30 has a cylindrical shape. A noncircular hole 34 is formed at a center of an upper end face of the head part 28. In the embodiment, the noncircular hole 34 has a quadrangle shape. A plurality of cutouts 36 is formed in an outer peripheral surface of the head part 28. The head part 28 has an outer diameter D3 greater than an outer diameter D4 of the neck part.

The engaging part 32 has a noncircular section. In the embodiment, the section is a substantially square. The engaging part 32 can pass through the first hole part 18 of the hole 16. The engaging part 32 is a quadrangular prism. A size c1 is the same as the outer diameter D4 of the neck part 30. A size d1 is greater than the outer diameter D4 of the neck part 30. A recessed part may be formed in a lower end face of the engaging part 32. A mass of the weight body Wt1 can be adjusted by a volume of a space formed by the recessed part. The size c1 and the size d1 will be described later.

The engaging part 32 has a corner part 32 a as a protruding part. The corner part 32 a protrudes to a direction (hereinafter, also referred to as an axial perpendicular direction) perpendicular to a center axis line of the weight body Wt1.

The engaging part 32 has an engaging surface 33. The engaging surface 33 is formed by a difference between the sectional shapes of the engaging part 32 and the neck part 30.

Preferably, the weight body Wt1 has a specific gravity greater than that of the socket sk1. In respect of durability and specific gravity, the material of the weight body Wt1 is preferably a metal. Examples of the metal include an aluminium alloy, a titanium alloy, stainless steel, a tungsten alloy, and a tungsten nickel alloy (W—Ni alloy).

FIG. 16 shows a non-engaging position NP and an engaging position EP of the weight body attaching/detaching mechanism M1. FIG. 16 is a bottom view of a state where the weight body Wt1 is inserted into the socket sk1.

As a relative relationship between the socket sk1 and the weight body Wt1, the non-engaging position NP and the engaging position EP can be taken. At the non-engaging position NP, the weight body Wt1 can be extracted from the socket sk1. On the other hand, at the engaging position EP, the weight body Wt1 cannot be extracted from the socket sk1. At the time of inserting the weight body Wt1 into the socket sk1, the relative relationship between the socket sk1 and the weight body Wt1 is the non-engaging position NP. The relative relationship makes the transition to the engaging position EP from the non-engaging position NP by rotation of a relative angle θ. The relative relationship returns to the non-engaging position NP from the engaging position EP by reverse rotation of the relative angle θ. In the weight body attaching/detaching mechanism M1, the weight body Wt1 can be attached/detached by merely applying the rotation of the angle θ. The weight body attaching/detaching mechanism M1 has excellent easiness of attachment/detachment.

In the embodiment, the angle θ is 45 degrees. The angle θ is not limited to 45 degrees. Examples of the angle θ include 30 degrees and 60 degrees.

An exclusive tool can be used in the weight body attaching/detaching mechanism M1. FIG. 17 is a perspective view showing a tool 60 as an example of the exclusive tool. The tool 60 is used for attaching/detaching the weight body Wt1. The tool 60 is provided with a handle 62, a shaft 64, and a tip part 66. The handle 62 has a handle body 68 and a holding part 70. The holding part 70 extends in a direction perpendicularly crossing with a rotation axis of the tool 60 from the first hole part of the handle body 68. The holding part 70 is provided with a holding body part 70 a and a lid 70 b.

A back end part of the shaft 64 is fixed to the holding body part 70 a. A section shape of the tip part 66 of the shaft 64 corresponds to a shape of the noncircular hole 34 of the weight body Wt1. In the embodiment, the tip part 66 has a quadrangle section. A pin 72 protrudes from a side surface of the tip part 66. The pin 72 is built in the tip part 66. Although not shown in the drawings, an elastic body (coil spring) is built in the tip part 66. The pin 72 is biased in a protruding direction by a biasing force of the elastic body.

When the weight body Wt1 is attached/detached, the lid 70 b is closed. A weight body housing part (not shown) is provided in the holding body part 70 a. Preferably, the weight body housing part can house the plurality of weight bodies Wt1. The weight bodies Wt1 can be taken out by opening the lid 70 b.

FIG. 18 is a view for describing an example of a method for attaching/detaching the weight body Wt1. FIG. 18( a) shows a state before the weight body Wt1 is attached. FIG. 18 (b) shows a state immediately after the weight body Wt1 is inserted. FIG. 18( c) shows a state where the weight body Wt1 is rotated and is fixed to the socket sk1. In each of FIGS. 18 (a), 18 (b) and 18 (c), the socket sk1 viewed from the bottom face side is shown on a right end.

The tip part 66 of the tool 60 is inserted into the noncircular hole 34 of the weight body Wt1 when the weight body Wt1 is attached. The pin 72 presses the noncircular hole 34 while going backward by the inserting. The weight body Wt1 is hardly dropped off from the tip part 66 by the pressing force.

As shown in FIGS. 18( a) and 18(b), the weight body Wt1 held by the shaft 64 of the tool 60 is inserted into the hole 16.

As shown in FIG. 18( b), the engaging part 32 of the weight body Wt1 passes through the first hole part 18 of the hole 16, and reaches to the second hole part 20. FIG. 18( b) shows the non-engaging position NP. The weight body Wt1 can be extracted from the hole 16 at the non-engaging position NP.

Next, relative rotation of an angle 8 (+θ) is performed. Specifically, the weight body Wt1 is rotated by the angle θ (+θ) with respect to the socket sk1 using the tool 60. The transition to the engaging position EP from the non-engaging position NP is attained by the rotation. FIG. 18 (c) shows the engaging position EP. The weight body Wt1 is fixed to the socket sk1 at the engaging position EP. At the engaging position EP, the weight body Wt1 is not separated by hitting.

When the weight body Wt1 is removed, reverse rotation of an angle θ is performed. In other words, rotation of an angle −θ is performed. The transition to the non-engaging position NP from the engaging position EP is attained by the rotation. The weight body Wt1 can be easily removed at the non-engaging position NP.

At the engaging position EP, the weight body Wt1 cannot be extracted from the hole 16. This is because the extraction of the weight body Wt1 is inhibited by engaging the step surface 22 of the hole 16 with the engaging surface 33 of the weight body Wt1 at the engaging position EP. The tool 60 can be easily extracted from the noncircular hole 34 of the weight body Wt1 at the engaging position EP.

As shown in FIGS. 13 and 16 or the like, the second hole part 20 of the hole 16 has a surface (non-engagement corresponding surface) 80 corresponding to the engaging part 32 at the non-engaging position NP, a surface (engagement corresponding surface) 82 corresponding to the engaging part 32 at the engaging position EP, and a resistance surface 84. The resistance surface 84 is pressed by (the corner part 32 a of) the engaging part 32 in the middle of the relative rotation between the non-engaging position NP and the engaging position EP. A frictional force is generated between the engaging part 32 and the second hole part 20 by the pressing. The resistance surface 84 is elastically deformed by the pressing. The material of the second hole part 20 is a comparatively hard polymer, and thereby the frictional force is increased. The increased frictional force generates strong rotation resistance. Strong torque is required for the mutual transition of the non-engaging position NP and the engaging position EP by the rotation resistance. Therefore, the tool 60 is required for the mutual transition. The mutual transition cannot be attained with empty hands without using the tool 60.

The weight body Wt1 located at the engaging position EP is not dropped off by strong impact in hitting.

Thus, the weight body can be attached/detached by merely performing the relative rotation of the angle θ in the weight body attaching/detaching mechanism M1.

As shown in the cross sectional view in FIG. 13, the socket sk1 includes an inner protruding part 19. The inner protruding part 19 is formed based on a difference between inner diameters of the first hole part 18 and the second hole part 20. The inner surface of the inner protruding part 19 is the first hole part 18.

At the engaging position EP, the inner protruding part 19 is sandwiched between the head part 28 and the engaging part 32. The inner protruding part 19 is sandwiched between the head part 28 and the engaging part 32 in a state where no clearance exists. Therefore, backlash of the weight body Wt1 is prevented at the engaging position EP.

The number N of the attaching/detaching mechanisms M1 is not limited. In respect of a degree of freedom for adjusting the position of the center of gravity of the head, the number N is preferably equal to or greater than 2.

[Hardness Hs of Second Hole Part of Socket]

In view of surely fixing the weight body Wt1 and of suppressing sounding in hitting, the hardness Hs of the socket sk1 is preferably equal to or greater than Shore D 40, more preferably equal to or greater than Shore D 45, still more preferably equal to or greater than Shore D 50, and yet still more preferably equal to or greater than Shore D 53. In respect of the easiness of attachment/detachment, the hardness Hs is preferably equal to or less than Shore D 58, more preferably equal to or less than Shore D 56, still more preferably equal to or less than Shore D 55, and yet still more preferably equal to or less than Shore D 54.

The hardness Hs is measured in accordance with regulation of “ASTM-D 2240-68” by using a Shore D type hardness scale attached to an automated rubber hardness measuring device (“P1” (trade name) manufactured by Koubunshi Keiki Co., Ltd.). The shape of a measurement sample is set to a cube having a side having a length of 3 mm. Measurement is performed under a temperature of 23° C. When possible, the measurement sample is cut out from (the second hole part of) the socket. When it is difficult to cut out the measurement sample, a measurement sample made of the same resin composition as that of (the second hole part of) the socket is used.

When a ball is hit by the golf club 2, hitting vibration is transmitted to golf player's hands via the golf club 2. The vibrational energy of the hitting vibration is transformed into the kinetic energy of the weight body Wt1 housed in the socket sk1. The socket sk1 and the weight body Wt1 transform the vibrational energy of the shaft 6 into the kinetic energy of the weight body Wt1, and thereby the hitting vibration can be alleviated.

[Polymer]

In respect of hardness, the material of the socket is preferably a polymer. Examples of the polymer include a thermosetting polymer and a thermoplastic polymer. Examples of the thermosetting polymer include a phenol resin, an epoxy resin, a melamine resin, a urea resin, an unsaturated polyester resin, an alkyd resin, a thermosetting polyurethane, a thermosetting polyimide, and a thermosetting elastomer. Examples of the thermoplastic polymer include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polytetrafluoroethylene, an ABS resin (acrylonitrile butadiene styrene resin), an acrylic resin, polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, polyether ether ketone, thermoplastic polyimide, polyamide imide, and a thermoplastic elastomer. Examples of the thermoplastic elastomer include a thermoplastic polyamide elastomer, a thermoplastic polyester elastomer, a thermoplastic polystyrene elastomer, a thermoplastic polyester elastomer, and a thermoplastic polyurethane elastomer.

In respect of durability, an urethane-based polymer and polyamide are preferable, and the urethane-based polymer is more preferable. Examples of the urethane-based polymer include polyurethane and a thermoplastic polyurethane elastomer. The urethane-based polymer may be thermoplastic, and may be thermosetting. In respect of formability, a thermoplastic urethane-based polymer is preferable, and the thermoplastic polyurethane elastomer is more preferable.

In respect of formability, the thermoplastic polymer is preferable. In respect of hardness and durability, in the thermoplastic polymer, the polyamide and the thermoplastic polyurethane elastomer are preferable, and the thermoplastic polyurethane elastomer is more preferable.

Examples of the polyamide include nylon 6, nylon 11, nylon 12, and nylon 66.

A preferable thermoplastic polyurethane elastomer contains a polyurethane component as a hard segment, and a polyester component or a polyether component as a soft segment. That is, preferable examples of the thermoplastic polyurethane elastomer (TPU) include a polyester-based TPU and a polyether-based TPU. Examples of a curing agent for the polyurethane component include cycloaliphatic diisocyanate, aromatic diisocyanate, and aliphatic diisocyanate.

Examples of the cycloaliphatic diisocyanate include 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI), 1,3-bis(isocyanatomethyl)cyclohexane (H₆XDI), isophorone diisocyanate (IPDI), and trans-1,4-cyclohexane diisocyanate (CHDI).

Examples of the aromatic diisocyanate include diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI). Examples of the aliphatic diisocyanate include hexamethylene diisocyanate (HDI).

Commercially available examples of the thermoplastic polyurethane elastomer (TPU) include “Elastollan” (trade name) manufactured by BASF Japan Ltd.

Specific examples of the polyester-based TPU include “Elastollan C70A”, “Elastollan C80A”, “Elastollan C85A”, “Elastollan C90A”, “Elastollan C95A”, and “Elastollan C64D”.

Specific examples of the polyether-based TPU include “Elastollan 1164D”, “Elastollan 1198A”, “Elastollan 1180A”, “Elastollan 1188A”, “Elastollan 1190A”, “Elastollan 1195A”, and “Elastollan ET385”. The polyether-based TPU is used in examples to be described later.

A fiber reinforced resin containing each of the polymers as a matrix may be used.

[Size c1]

A distance between opposed surfaces of the engaging part 32 is shown by a double pointed arrow c1 in FIG. 15. The size c1 is equal to a length of a side of a square obtained by eliminating the roundness of a corner existing in the section of the engaging part 32.

[Size d1]

A longest sectional size of the engaging part 32 is shown by a double pointed arrow d1 in FIG. 15. In the embodiment, the size d1 is a length of a diagonal line of the section (substantially square) of the engaging part 32. The size d1 is a length of a longest cross line Lm (see FIG. 15) of the engaging part 32. Both end points of the longest cross line Lm are shown by symbol p1 in FIG. 15. These points p1 are peaks in the section of the engaging part 32.

[Size F1]

A distance between resistance surfaces 84 opposed to each other is shown by a dashed line double pointed arrow F1 in FIG. 14. The size F1 is measured at a position where elastic deformation is maximized in the mutual transition. The size F1 is correlated with the maximum value of torque required in the mutual transition.

[Size K1]

An opening width of the first hole part 18 of the hole 16 is shown by a double pointed arrow K1 in FIG. 14. The size K1 is equal to a length of a side of a square obtained by eliminating the roundness of a corner existing in the section of the first hole part 18.

[Size G1]

Across length of the second hole part 20 between positions with which both the end points p1 of the longest cross line Lm are brought into contact at the engaging position EP is shown by a double pointed arrow G1 in FIG. 14.

[Size H1]

A length of a shortest cross line Lh of the second hole part 20 is shown by a dashed line double pointed arrow H1 in FIG. 14. Both end points p2 of the shortest cross line Lh are boundary points between an engagement corresponding surface 82 and a non-engagement corresponding surface 80.

[F1/d1]

In respect of suppressing the scraping of the inner surface of the socket when the weight body Wt1 is attached/detached, a ratio (F1/d1) is preferably equal to or greater than 0.935, more preferably equal to or greater than 0.940, and still more preferably equal to or greater than 0.945. In view of surely fixing the weight body Wt1 and of suppressing sounding in hitting, the ratio (F1/d1) is preferably equal to or less than 0.965, more preferably equal to or less than 0.960, and still more preferably equal to or less than 0.955.

In the middle of the relative rotation, the amount of deformation of the resistance surface 84 is maximized. As the maximum amount of the deformation is greater, the ratio (F1/d1) is less.

[G1/d1]

In respect of suppressing the scraping of the inner surface of the socket when the weight body Wt1 is attached/detached, a ratio (G1/d1) is preferably equal to or greater than 0.987, more preferably equal to or greater than 0.989, and still more preferably equal to or greater than 0.991. In view of surely fixing the weight body Wt1 and of suppressing sounding in hitting, the ratio (G1/d1) is preferably equal to or less than 0.996, more preferably equal to or less than 0.995, and still more preferably equal to or less than 0.994.

[K1−c1]

When a difference (K1−c1) is excessively small, the catching of the weight body Wt1 is apt to be caused when the weight body Wt1 is extracted. Therefore, the smoothness of attachment/detachment may be inhibited. In respect of easily extracting the weight body Wt1 at the non-engaging position NP, the difference (K1−c1) is preferably equal to or greater than 0.3 mm, more preferably equal to or greater than 0.35 mm, and still more preferably equal to or greater than 0.4 mm.

In the embodiment, a part of the inner surface of the second hole part 20 is flush with the inner surface of the first hole part 18. The flush portion is the non-engagement corresponding surface 80. When the difference (K1−c1) is excessively large in the design of the hole 16, the size F1 and/or the size G1 are/is apt to be increased. In this case, the holding force of the weight body Wt1 may be reduced to cause sounding in hitting. In this respect, the difference (K1−c1) is preferably equal to or less than 0.6 mm, more preferably equal to or less than 0.55 mm, and still more preferably equal to or less than 0.5 mm.

[H1/d1]

When a ratio (H1/d1) is too small, the size G1 and/or the size F1 is also apt to be small. In this case, the scraping of the inner surface of the second hole part 20 is apt to be caused. In this respect, the ratio (H1/d1) is preferably equal to or greater than 0.785, more preferably equal to or greater than 0.810, and still more preferably equal to or greater than 0.840.

When the torque is too strong in the transition to the engaging position EP from the non-engaging position NP, the excessive rotation of the weight body Wt1 may be caused. The weight body Wt1 may pass through the engaging position EP, and may reach to the non-engaging position NP by the excessive rotation although the transition to the engaging position EP is intended. The excessive rotation of the weight body Wt1 is suppressed by decreasing the size H1. In respect of suppressing the excessive rotation, the ratio (H1/d1) is preferably equal to or less than 0.915, more preferably equal to or less than 0.890, and still more preferably equal to or less than 0.870.

Under an environment of 40° C., a maximum torque (N·m) required in attaching/detaching is defined as T40. Under an environment of 25° C., the maximum torque (N·m) required in attaching/detaching is defined as T25. Under an environment of 5° C., the maximum torque (N·m) required in attaching/detaching is defined as T5. In view of enabling smooth attachment/detachment regardless of a temperature, a ratio (T40/T5) is preferably equal to or greater than 0.30, more preferably equal to or greater than 0.35, still more preferably equal to or greater than 0.40, and yet still more preferably equal to or greater than 0.41.

The maximum torque required in attaching/detaching may depend on a temperature environment. As the temperature is lower, the maximum torque is apt to be increased.

In view of enabling smooth attachment/detachment regardless of a temperature, a ratio (T25/T5) is preferably equal to or greater than 0.57, more preferably equal to or greater than 0.60, and still more preferably equal to or greater than 0.61.

Because of the dependency on temperature, the ratio (T40/T5) and the ratio (T25/T5) are normally equal to or less than 1.

In respect of enabling smooth attachment/detachment at a low temperature, the maximum torque T5 is preferably equal or less than 6.3 (N·m), more preferably equal or less than 6.0 (N·m), still more preferably equal or less than 5.5 (N·m), and yet still more preferably equal or less than 5.0 (N·m).

In respect of ensuring fixation at a high temperature, the maximum torque T40 is preferably equal to or greater than 1.0 (N·m), more preferably equal to or greater than 1.5 (N·m), and still more preferably equal to or greater than 1.8 (N·m).

FIG. 19 is an exploded perspective view of a weight body attaching/detaching mechanism M2 according to another embodiment. The weight body attaching/detaching mechanism M2 is provided with a socket sk2 and the weight body Wt1. Furthermore, the weight body attaching/detaching mechanism M2 has a bottom face forming part 13. The bottom face forming part 13 may not exist.

As shown in FIG. 19, the socket sk2 has an interposition part 11 and a hole 16. The interposition part 11 constitutes the upper part of the socket sk2. The interposition part 11 constitutes a portion placed on the most sole surface side in the socket sk2. The interposition part 11 extends toward an upper side (sole surface side) from an opening surface f1 of the hole 16. The interposition part 11 is cylindrical. The inner surface 11 a of the interposition part 11 is a circumferential surface. The outer surface 11 b of the interposition part 11 is a circumferential surface.

The socket sk2 is fixed in the recessed part R. The fixation is attained by an adhesive, for example. The weight body Wt1 is detachably attached to the socket sk2. Therefore, the weight body Wt1 can be attached/detached to/from the head 4.

FIG. 20 is a perspective view of the socket sk2. FIG. 20 is a perspective view of the socket sk2 viewed from a bottom face side. FIG. 21 shows a plan view of the socket sk2, a cross-sectional view of the socket sk2, and a bottom view of the socket sk2 in this order from the top. The cross-sectional view of FIG. 21 is a cross-sectional view taken along line A-A of the plan view of FIG. 21.

The socket sk2 is the same as the socket sk1 except the existence of the interposition part 11.

The weight body Wt1 has an exposed part E1 (see FIG. 19). In the embodiment, the head part 28 is the exposed part E1. The exposed part E1 does not independently contribute to the retention of the weight body Wt1. In other words, the exposed part E1 does not independently attain the retention.

The opening surface f1 and the step surface 22 which are shown in FIG. 21 are sandwiched between the exposed part E1 and the engaging part 32 at the engaging position EP, and thereby the movement in the insertion direction of the weight body Wt1 is regulated.

The exposed part E1 is located on the outermost side (sole surface side) of the weight body Wt1. A state where the weight body Wt1 is placed at the engaging position EP is also referred to as an attached state. In the attached state, the exposed part E1 is exposed to the outside.

[Interposition Part]

In the attached state, the interposition part 11 is interposed in at least a part between the exposed part E1 and the head body h1. In the embodiment, the interposition part 11 is cylindrical. In the embodiment, the interposition part 11 exists over the whole periphery of the exposed part E1. Therefore, the effect caused by the interposition part 11 is enhanced. The interposition part 11 may be disposed in only a part of the periphery of the exposed part E1.

In the attached state, the interposition part 11 is not engaged with the weight body Wt1. In the attached state, the interposition part 11 is not engaged with the exposed part E1. Even when the interposition part 11 is brought into contact with the weight body Wt1, the interposition part 11 has no effect of stopping the weight body Wt1 in an engaged state. The interposition part 11 does not fix the weight body Wt1.

The impact shock caused by hitting can vibrate the weight body Wt1. The amplitude of the vibration is apt to be increased in the exposed part E1 (head part 28). This is because the exposed part E1 is in a state where it is apt to be comparatively moved without being engaged with the interposition part 11. The interposition part 11 can effectively absorb the vibration of the exposed part E1. Impact shock absorbing performance can be improved by suppressing the vibration of a portion (exposed part E1) which is likely to be vibrated. The impact shock absorbing performance can contribute to improvement in hit ball feeling. The hit ball feeling can be improved by the interposition part 11. Since the interposition part 11 does not fix the weight body Wt1, the interposition part 11 is likely to be deformed. Therefore, the vibration absorbing performance can be effectively improved by the interposition part 11.

FIG. 22 is a cross-sectional view of a weight body Wt10 of a modification. FIG. 23 is a cross-sectional view of a weight body attaching/detaching mechanism M3 when the weight body Wt10 is in an attached state. The principle of the weight body attaching/detaching mechanism M3 is the same as that of the weight body attaching/detaching mechanism M2.

The weight body attaching/detaching mechanism M3 is provided with a socket sk20 and the weight body Wt10. The head body m5 is provided with a recessed part 140. The shape of the recessed part 140 corresponds to that (outer shape) of the socket sk20. The inner diameter of the recessed part 140 is substantially equal to the outer diameter of the socket sk20. The outer surface of the socket sk20 is bonded to the inner surface of the recessed part 140. An outer peripheral surface 100 a of the socket sk20 is bonded to an inner peripheral surface 140 a of the recessed part 140.

The recessed part 140 is formed by a recessed-part forming member b5. The recessed-part forming member b5 is a separate member from the head body m5.

The recessed-part forming member b5 is fixed to an opening hs5 for a recessed part. The fixation is attained by welding.

As shown in FIG. 23, the socket sk20 has an interposition part 110. The interposition part 110 constitutes the upper part of the socket sk20. The interposition part 110 constitutes a portion placed on the most sole surface side in the socket sk20. The interposition part 110 is cylindrical.

As shown in FIG. 22, the weight body Wt10 has a head part 280, a neck part 300, and an engaging part 320. The neck part 300 has a cylindrical shape. A noncircular hole 340 is formed at a center of an upper end face of the head part 280. As in the noncircular hole 34, the sectional shape (the shape of the section taken along line A-A of FIG. 22) of the noncircular hole 340 is a substantially quadrangle.

The weight body Wt10 has an exposed part E1. In the embodiment, the head part 280 is the exposed part E1.

The exposed part E1 is located on the outermost side (sole surface side) of the weight body Wt10. In the attached state, the exposed part E1 is exposed to the outside (see FIG. 23).

A clearance distance X1 between the exposed part E1 (head part 280) and the head body m5 is equal to a thickness B2 of the interposition part, or greater than the thickness B2. That is, X1≧B2 is set. The thickness B2 of the interposition part is measured in a natural state where the socket sk20 is independently left. If a difference (X1−B2) is small, a foreign matter is less apt to enter. In this respect, the difference (X1−B2) is preferably equal to or less than 0.3 mm, and more preferably equal to or less than 0.2 mm. Meanwhile, if the difference (X1−B2) is excessively small, workability for attaching/detaching the weight body may be decreased. In this respect, the difference (X1−B2) is preferably equal to or greater than 0.05 mm, and more preferably equal to or greater than 0.075 mm.

There are differences between the weight body Wt1 and the weight body Wt10. A first difference is the length L11 of the engaging part 320 (see FIG. 22). The length L11 of the engaging part 320 is shorter than that of the engaging part 32. The engaging part 320 is flatter than the engaging part 32. As a result, a full length Lw of the weight body Wt10 is shorter than that of the weight body Wt1. The full length Lw of the weight body Wt10 is a length along the insertion direction. A second difference is that a recessed part 340 a is formed in the inner surface of the noncircular hole 340. The recessed part 340 a provides a space to which the pin 72 of the tool 60 protrudes. If the shaft 64 of the tool 60 is inserted into the noncircular hole 340, the pin 72 protrudes in the recessed part 340 a. The pin 72 is engaged with the recessed part 340 a by the protrusion. The shaft 64 is less apt to be pulled out of the noncircular hole 340 by the engagement. Therefore, the attaching/detaching work of the weight body Wt10 can be smoothly performed.

As shown in FIG. 22, the space r1 is provided in the engaging part 320. A weight W1 of the weight body can be changed without changing the outer shape of the weight body Wt10 by adjusting the volume of the space r1. Furthermore, the weight W1 of the weight body can be changed without changing the outer shape of the weight body Wt10 by changing the material of the weight body Wt10. Therefore, a plurality of weight bodies Wt10 having different weights W1 and the same outer shape can be prepared. Therefore, the weight bodies Wt10 having different weights W1 can be attached to the same socket sk20.

In respect of appearance, it is preferable that an end face 110 c of the interposition part 110 does not protrude to the outside with respect to an end face 120 c of the weight body Wt10.

In FIG. 23, the weight body Wt10 is in an attached state. In the attached state, the interposition part 110 does not protrude to the outside with respect to the weight body Wt10 (an upper side in FIG. 23). The appearance can be improved by the non-protrusion. A grounding resistance on a sole surface can be suppressed by the non-protrusion.

In the attached state, a full length S1 of the socket sk20 is equal to or less than a depth HL of the recessed part 140 (S1≦HL). The interposition part 110 does not protrude to the outside of the recessed part 140. As shown in FIG. 23, the end face 110 c of the interposition part 110 is located on an inner side in an insertion direction (a lower side in FIG. 23) with respect to an opening edge 140 b of the recessed part 140. The appearance can be improved by the non-protrusion. The grounding resistance on the sole surface can be suppressed by the non-protrusion.

In the attached state, the weight body Wt10 does not protrude to the outside of the recessed part 140. As shown in FIG. 23, the end face 120 c of the weight body Wt10 is located on the inner side in the insertion direction (a lower side in FIG. 23) with respect to the opening edge 140 b of the recessed part 140. The appearance may be improved by the non-protrusion. The grounding resistance on the sole surface is suppressed by the non-protrusion, and the weight body Wt10 is less apt to fall off. The adhesion of the foreign matter can be suppressed by the non-protrusion.

In the embodiment of FIG. 23, an adhesion area between the recessed part 140 and the socket sk20 is secured while the depth HL and the full length S1 are suppressed. Therefore, the fixing strength of the socket sk20 is high. Since the depth HL is suppressed, a degree of freedom in design of the head is improved. In the fairway wood, the utility type head, and the hybrid type head or the like, a head maximum thickness Th is small. Since the depth HL and the full length S1 are small in the embodiment, the embodiment can be preferably applied to also a head having a small head maximum thickness Th.

The grounded ball is often hit by the fairway wood, the utility type head, and the hybrid type head or the like unlike a driver. Therefore, foreign matters such as sand, soil, and grass are apt to adhere. In the embodiment of FIG. 23, a clearance between the exposed part E1 and the recessed part 140 is decreased by the existence of the interposition part 110. Therefore, the entering of the foreign matter to the clearance is suppressed.

A length in an insertion direction of the interposition part 110 is shown by symbol B1 in FIG. 23. When the length B1 is excessively small, a clearance between the exposed part E1 (head part 280) and the head body m5 is apt to be generated. Foreign matters such as mud, soil, sand of a bunker, and grass may enter the clearance. The foreign matter decreases the appearance. When the length B1 is excessively small, sounding may be caused. The sounding is caused by contact between the weight body Wt10 and the head body m5. Furthermore, when the length B1 is excessively small, the adhesion area between the socket sk20 and the recessed part 140 is decreased. In these respects, the length B1 is preferably equal to or greater than 0.5 mm, more preferably equal to or greater than 1.0 mm, and still more preferably equal to or greater than 1.5 mm. When the length B1 is excessively large, the depth HL of the recessed part 140 is increased. The excessive depth HL decreases the degree of freedom in the design of the head. In a head having a small head height (a so-called shallow head), the depth HL has restrictions. When the length B1 is excessively large, the interposition part 110 is apt to be brought into contact with the ground. In these respects, the length B1 is preferably equal to or less than 5 mm, more preferably equal to or less than 4.5 mm, and still more preferably equal to or less than 4 mm.

A thickness of the interposition part 110 is shown by symbol B2 in FIG. 23. When the thickness B2 is excessively small, formability is decreased. If the thickness B2 is excessively small, the interposition part 110 is apt to be deformed when the weight body is inserted. The insertion of the weight body may not be smoothed by the deformation. In these respects, the thickness B2 is preferably equal to or greater than 0.4 mm, more preferably equal to or greater than 0.5 mm, and still more preferably equal to or greater than 0.6 mm. When the weight of the socket sk20 is excessively large, a degree of freedom in design of the weight body and the head may be constrained. In this respect, the thickness B2 is preferably equal to or less than 1 mm, more preferably equal to or less than 0.9 mm, and still more preferably equal to or less than 0.8 mm.

An outer diameter of the socket sk20 is shown by symbol B3 in FIG. 23. In the embodiment, the outer diameter of the socket sk20 is substantially equal to that of the interposition part 110. If the outer diameter B3 of the interposition part is excessively small, it may become difficult to design and manufacture the weight body. If the outer diameter B3 of the interposition part is excessively small, the adhesion area between the socket sk20 and the recessed part 140 is decreased. In these respects, the outer diameter B3 is preferably equal to or greater than 13 mm, more preferably equal to or greater than 13.5 mm, and still more preferably equal to or greater than 14 mm. When the inner diameter of the recessed part 140 is excessively large, a degree of freedom in design of the head is constrained. When the outer diameter B3 is excessively large, the formability of the socket sk20 may be decreased. In these respects, the outer diameter B3 is preferably equal to or less than 25 mm, more preferably equal to or less than 20 mm, and still more preferably equal to or less than 16 mm.

A full length in an insertion direction of the socket sk20 is shown by symbol S1 in FIG. 23. In respect of increasing an adhesion area between the socket sk20 and the head body m5, the full length S1 is preferably equal to or greater than 5 mm, and more preferably equal to or greater than 6 mm. When the full length S1 is excessively large, the depth HL becomes excessively large. In this case, the position of a center of gravity of the head body m5 is apt to become high. When the full length S1 is excessively large, the weight of the socket sk20 becomes excessively large, which may constrain the design in the position of the center of gravity of the head. In these respects, the full length S1 is preferably equal to or less than 13 mm, and more preferably equal to or less than 12 mm.

A part of the crown 6 is illustrated in the cross sectional view of FIG. 23. The crown 6 is a part of the head body m5.

A shortest distance between an inner surface 6 a of the crown 6 and the socket sk20 is shown by a double pointed arrow T1 in FIG. 23. In respect of productivity, the shortest distance T1 is preferably equal to or greater than 5 mm. When the shortest distance T1 is small, it is difficult to perform the recessed-part integral forming particularly in a head produced by casting. This problem is as described above. The problem can be solved by forming the recessed-part forming member b5 separately from the head body m5. Therefore, when the shortest distance T1 is small, separately forming the recessed-part forming member possess great significance. In this respect, the shortest distance T1 is preferably equal to or less than 30 mm, and more preferably equal to or less than 20 mm.

When the volume of the hollow part of the head is small, the recessed part is apt to hamper the productivity. Particularly, when the head body is manufactured by casting, this tendency becomes pronounced. When the volume of the hollow part of the head is small, the recessed part on the outer surface of the head is a protrusion part on the inside of the head. The protrusion part makes the extraction of the core difficult in manufacturing the wax mold, for example. Therefore, the structure of forming the recessed-part forming member separately from the head body is effective when the head volume is small. In this respect, the head volume is preferably equal to or less than 250 cc, more preferably equal to or less than 200 cc, and still more preferably equal to or less than 180 cc. In respect of enhancing a moment of inertia of the head, the head volume is preferably equal to or greater than 100 cc, and more preferably equal to or greater than 120 cc.

In respect of enhancing an effect of weight adjustment, the weight W1 of the weight body is preferably equal to or greater than 1 g, more preferably equal to or greater than 1.5 g, and still more preferably equal to or greater than 2 g. When the weight W1 is excessively large, a large centrifugal force acts on the weight body. The large centrifugal force increases a load to the socket. In this respect, the weight W1 of the weight body is preferably equal to or less than 15 g, more preferably equal to or less than 14 g, and still more preferably equal to or less than 13 g.

The weight body attaching/detaching mechanism satisfies the Golf Rules defined by R&A (Royal and Ancient Golf Club of Saint Andrews). That is, the weight body attaching/detaching mechanism satisfies requirements specified in “1b Adjustability” in “1 Clubs” of “Appendix II Design of Clubs” defined by R&A. The requirements defined by the “1b Adjustability” are the following items (i), (ii), and (iii):

(i) the adjustment cannot be readily made;

(ii) all adjustable parts are firmly fixed and there is no reasonable likelihood of them working loose during a round; and

(iii) all configurations of adjustment conform with the Rules.

Examples

Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be interpreted in a limited way based on the description of examples.

Example

Ahead that is the same as the head 4 was produced. Ahead body was produced by casting. The material of the head body was a maraging steel. A lost-wax casting process was adopted in the casting. A recessed-part forming member was produced separately from the head body. The recessed-part forming member was produced by casting. The material of the recessed-part forming member was CUSTOM 450 (manufactured by Carpenter Technology Corporation). A face plate was produced by forging. The recessed-part forming member was welded to an opening for a recessed part of the head body. In addition, the face plate was welded to an opening part provided on a face part of the head body. The weight body attaching/detaching mechanism shown in FIG. 11 was attached to a first recessed part and a second recessed part. Thus, a head of example was obtained. In the head, a head volume was 155 cc; a real loft angle was 15 degrees; a lie angle was 58 degrees; and a face angle was plus 1 degree (1 degree open). A head thickness was 37 mm. The shortest distance T1 was 15 mm. In the example, although the hollow part of the head was small and the shortest distance T1 was small, the recessed parts were accurately formed.

INDUSTRIAL APPLICABILITY

The present invention described above can be applied to all golf clubs. The present invention can be used for a wood type club, a utility type club, a hybrid type club, an iron type club, and a putter club or the like.

DESCRIPTION OF THE REFERENCE CHARACTERS

-   -   4 . . . head     -   6 . . . crown     -   8 . . . sole     -   R, R1, R2, R3 . . . recessed part     -   b1, b3, b4, b5 . . . recessed-part forming member     -   m1, m3, m5 . . . head body     -   M1, M2, M3 . . . weight body attaching/detaching mechanism     -   x1 . . . receiving part     -   y1 . . . outer extension part     -   hs1 . . . opening for a recessed part     -   16 . . . hole of socket     -   18 . . . first hole part     -   20 . . . second hole part     -   30 . . . neck part     -   32 . . . engaging part     -   33 . . . engaging surface     -   60 . . . tool     -   80 . . . non-engagement corresponding surface     -   82 . . . engagement corresponding surface     -   84 . . . resistance surface     -   NP . . . non-engaging position     -   EP . . . engaging position 

1. A hollow golf club head comprising a head body and a recessed-part forming member, wherein the head body includes an opening for a recessed part and a receiving part formed on at least a part of a periphery of the opening for a recessed part, the recessed-part forming member is fixed to the opening for a recessed part, and a recessed part is formed on an outer surface of the head by the recessed-part forming member, the recessed-part forming member is formed separately from the head body, the recessed-part forming member includes an outer extension part, and the outer extension part is supported by the receiving part.
 2. The golf club head according to claim 1, wherein the head body includes a sole and a crown, the head body is produced by casting, the recessed-part forming member is attached to the sole, and a shortest distance T1 between the recessed-part forming member and the crown is equal to or less than 30 mm.
 3. The golf club head according to claim 1 further comprising a weight body, wherein the weight body is disposed on the recessed part in a detachable state.
 4. The golf club head according to claim 3, further comprising a socket, wherein the socket is fixed in the recessed part, relative rotation of an angle θ can be performed between the weight body and the socket, the weight body can be attached to the socket by a rotation of the angle θ, and the weight body can be detached from the socket by a reverse rotation of the angle θ.
 5. The golf club head according to claim 1, wherein the recessed part has a groove shape.
 6. The golf club head according to claim 1, wherein a toe-heel directional length of the recessed part is equal to or greater than 30 mm, and a width of the recessed-part forming member is equal to or less than 25 mm, the width being measured along a face-back direction.
 7. The golf club head according to claim 6, wherein a cross section along a face-back direction of the recessed-part forming member is smoothly continuous. 